Micro lab quiz 5

  1. What is a carbohydrate fermentation media?  What information does it provide?
    • Broth media with phenol red
    • basic
    • if sugar is fermented, acid forms, Phenol red changes color
  2. what is phenol red and why is it used in fermentation tests?
    • pH indicator
    • turns yellow when pH is lowered -> indicates fermentation
  3. What is a Durham tube?  What information does it provide?
    indication of gas production
  4. What is superoxide dismutase?
    catalyzes conversion of superoxide radicals (O2-) to hydrogen peroxide
  5. what is the catalase test/what does catalase do?  What information does it provide/what indicates a positive result?
    Catalase breaks down hydrogen peroxide (H2O2) to water and gaseous oxygen

    • Positive result: bubbles -> presence of catalase
    • positive: microcaccae
    • negative: streptocaccae
  6. What is the nitrate reduction test?  What information does it provide?
    Differentiates Enterobacteriaceae from Gram negative rods that don't reduce nitrate or reduce it past nitrite

    Tells us if the organism reduces nitrate to nitrite
  7. What type of media is Phenylethyl Alcohol Agar (PEA) test?
    What does it test for?
    Isolates what two organisms?
    • undefined, selective
    • encourages Gram positive organisms
    • Phenylethyl Alcohol inhibits Gram negative organisms by breaking down their membrane
    • Isolates stapylococci and streptococci
  8. What type of media is Mannitol Salts Agar (MSA) Test and what info does it provide?
    positive result?
    • differential and selective
    • Selects for staphylococcus aureus
    • -bright yellow colonies with yellow halo
  9. What type of media is the MacConkey Agar (Mac) Test?  What info does it provide? positive result?
    differentiates between members of _____
    • selective and differential
    • isolate and differentiate between different members of Enterobacteriacae
    • based on ability to ferment lactose
    • positive: turns pink -> can ferment lactose
  10. Eosin methylene Blue (EMB) Agar test
    isolates what organism/organisms that do what?
    • complex, selective, differential
    • inhibits Gram positive
    • isolate fecal coliforms
    • lactose fermenters change color
    • E. coli = dark purple/black with green sheen
  11. Hektoen Enteric Agar (Hek) Test
    isolates what two organisms
    complex, moderately selective, differential

    Isolate salmonella (black) and shigella (blue-green)
  12. Xylose Lysine Desoxycholate (XLD) Test
    Isolates what two organisms
    Shigella and Providencia

    decarboxylate lysine -> red
  13. Blood Agar Test for Hemolysis isolates/cultivates _________
    detects presence of _______________
    • fastidious bacteria
    • hemolysins
  14. Enterotube is good for __________ identification of enterobacteriaceae
    rapid identification
Card Set
Micro lab quiz 5
Micro lab quiz #5